As for the solid laser, semiconductor laser and gas laser each emitting an ultraviolet ray, a visible ray or an infrared ray at a wavelength of from 300 to 1,200 nm, high-output and compact lasers are now easily available. These lasers are very useful as a light source for recording at the time of directly producing a printing plate based on digital data of a computer or the like. Studies on the recording material sensitive to these various laser rays are being diversely made and representative examples of such a recording material include the followings. First, an acid catalyst crosslinking-type negative recording material having a sensitivity at a wavelength of 760 nm or more and being recordable by an infrared laser is known (sea, for ale, JP-A-8-276558 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)). Secondly, a large number of radical polymerization-type negative recording materials which are a recording material sensitive to an ultraviolet or visible laser of 300 to 700 nm are known (see, for example, U.S. Pat. No. 2,850,445 and JP-B-44-20189 (the term “JP-B” as used herein means an “examined Japanese patent publication”)).
On the other hand, a polymerizable composition recordable by a short-wavelength ray of 300 nm or less or an electron beam is important particularly as a photoresist material. The integration degree of integrated circuits has recently become higher and higher, and also in the production of a semiconductor substrate for VLSI or the like, processing of an ultrafine pattern having a line width of a half micron or less is required. In order to satisfy such a requirement, the wavelength used in an exposure apparatus for photolithography becomes shorter and studies are being made to use a far ultraviolet ray or an excimer laser ray (e.g., XeCl, KrF, ArF) and furthermore to form an ultrafine pattern by an electron beam. Particularly, the electron beam is promising as a light source for pattern-formation techniques in the next generation.
These image-forming materials all have a common problem to be solved and this is how to expand the image ON-OFF in the areas irradiated and not irradiated with the above-described various energies.
In order to solve this problem, a large number of reports using a high-sensitivity radical polymerizable composition have been proposed and the main components used in such a radical polymerizable composition are generally a radical polymerizable crosslinking agent and a polymer binder. As for the radical polymerizable crosslinking agent, a polyfunctional crosslinking agent having two or more polymerizable groups within the molecule is usually used to enhance the crosslinking efficiency. However, the reaction rate of the radical polymerizable crosslinking agent is not so high in practice and there is a fear that an unreacted crosslinking agent or crosslinking group remains in the laser exposed area and due to its presence, the film property in the region cured by exposure is deteriorated.
When a highly reactive polymerizable crosslinking agent is used or the polymerizable crosslinking agent content is increased for the purpose of obtaining high sensitivity, the storage stability of the polymerizable composition tends to decrease due to high reactivity. In order to satisfy both the storage stability and the high sensitivity, the balance therebetween is taken at present by controlling the reactivity or content of the crosslinking group.
In order to form a highly curable film, a novel aromatic ester (meth)acrylate dendrimer useful as a polymerizable compound, and a curable resin composition comprising this polymerizable compound and a polymerization initiator have been proposed (see, for example, JP-A-11-60540). The (meth)acrylate dendrimer used in this composition is called an “aromatic ester” and contains many phenyl groups within the molecule to render the entire molecule hydrophobic. Therefore, a coat having excellent water resistance can be formed, but the hydrophobicity is too high in view of removing an unnecessary coat by performing development. Thus, this composition cannot be substantially used for pattern-forming materials such as image-forming material.